The present invention relates to a radiator screen device that prevents a radiator for an industrial vehicle including a construction machine and an agricultural machine from being clogged. The invention also relates to a radiator screen unit that includes the radiator screen device and a fan, and an industrial vehicle having the radiator screen unit.
An industrial vehicle such as a forklift truck is driven by an internal combustion engine having a radiator for cooling coolant circulating in the engine. Unlike general vehicles, in the case of an industrial vehicle such as a construction machine and an agricultural machine, the effect of cooling the internal combustion engine operating under a high load by the wind of air caused by traveling of the vehicle cannot be expected. In order to provide effective cooling, a flow of cooling air with a wind velocity of about 10 meters per second is generated by using a fan so as to flow through the radiator. Dust accumulated in the radiator causes the radiator to be clogged, which prevents the coolant to be cooled appropriately. As a result, the internal combustion engine may overheat. It is noted that the term of industrial vehicle appearing in the description includes a construction machine and an agricultural machine.
An industrial vehicle such as a forklift truck may be operated in a dusty environment. For example, in a wood processing factory, a forklift truck is operated in an environment in which a large amount of stringy wood debris of various sizes is present on the floor. The industrial vehicle working in such an environment tends to overheat because of the radiator being clogged with dust. When the engine is overheated, it is difficult for an operator to remove and clean the radiator. To prevent such trouble, in general, a screen is disposed upstream of the radiator so as to capture dust. In the event of an overheat, the operator may remove and clean the screen. The screen needs to be cleaned periodically. Since the industrial vehicle remains idle during cleaning of the screen, it is desired to reduce the cleaning frequency for improving the working efficiency of the vehicle.
Japanese Patent Application Publication No. 2016-10766 (JP '766) discloses an air-intake device for preventing foreign substances from being taken in with the air. The air-intake device has a rotatable conical filter formed of a perforated plate. The conical filter is driven by a motor and a fan is connected to the filter for rotation therewith. Cleaning of the filter is accomplished by removing dust by centrifugal force of the rotating filter and scraping foreign substances accumulated on the surface of the rotational filter by using cleaning blades. Thus, cleaning of the rotating filter is performed automatically.
Japanese Patent Application Publication No. 2002-58939 (JP '939) discloses an exhaust gas purifying apparatus including a plurality of plate filters that are laminated in the direction in which exhaust gas containing particulates flows. Each plate filter is perforated or has therein small holes that are formed bored in the direction in which exhaust gas flows. The holes are formed through the respective plate filters so that the size of the holes is reduced in the flowing direction of the exhaust gas. Thus, particulates of various sizes are dispersedly captured by the respective plate filters so that clogging of the filters in a short time is prevented.
The intake device of JP '766 that removes foreign substances by centrifugal force and by scraping foreign substances from the surface of the rotating conical filter by using cleaning blades is disadvantageous over a plate filter in that the filter of a conical shape occupies a larger space. In the structure in which foreign substances are removed by centrifugal force, the entire radiator need be covered so that foreign substances flown by centrifugal force are prevented from flowing into the radiator, with the result that a large space is required in a vehicle for mounting the rotational conical filter. Furthermore, in order for the circular shape of the rotational filter as seen in front view thereof to cover the rectangular upstream surface of a radiator, the rotational filter needs an area that is considerably larger than the area of the upstream surface of the radiator, which makes the rotational filter difficult to be installed in an industrial vehicle.
In the case of the exhaust purification apparatus of JP '939 having a plurality of the plate filters having mesh sizes that are different from one of filter from another, each plate filter captures particulates of a predetermined range of sizes. If the particulate size distribution is uniform, the particulate of various sizes may be captured uniformly by the filters. If particulates of any specific range of sizes are larger, the plate filter corresponding to the specific range of size is clogged earlier than other plate filters.
The present invention which has been made in light of the above problems is directed to providing a radiator screen device that presents a radiator for an industrial vehicle including a construction machine and an agricultural machine from being clogged with substances in the form of a string and having different lengths and that prolongs the time before the engine overheats and hence the operation time of the industrial vehicle. The present invention is directed also to providing a radiator screen unit that includes the radiator screen device and a fan, and to providing an industrial vehicle that has the radiator screen unit and saves the installation space in the industrial vehicle.